1. Field of the Invention
This specification relates to a mobile terminal having an antenna capable of transmitting and receiving wireless electromagnetic waves.
2. Description of Related Art
Mobile communication services are evolving with development of mobile communication technologies and consumers' demands on more various services. Initial mobile communications are merely provided by focusing on voice communications. However, various mobile communication services, such as a multimedia service like music or movie, a wireless Internet service allowing use of Internet at ultrahigh speed even during movement and a satellite communication service providing mobile communications beyond borders, have appeared in recent time. In addition, various mobile communication service methods, such as Personal Communication Services (PCS), Wideband Code Division Multiple Access (WCDMA), ultra wideband mobile communication such as Ultra-wideband (UWB) as well as the existing cellular communication service method, are on the rise.
If such various mobile communication services are provided to one mobile communication terminal at various frequency bands, it may increase convenience and efficiency of the services. Accordingly, broadband wireless terminals have widely been used in recent time, and a technology, which will allow an antenna as one of essential elements of a wireless terminal to operate in a broadband, is requested.
Meanwhile, a typical mobile communication terminal has several disadvantages of lowering of antenna radiation efficiency, narrowing of frequency bands and reduction of an antenna gain, due to a size-reduction of the antenna of the mobile communication terminal. However, in spite of such function degradation, the mobile communication terminal is kept required to be reduced in size, multifunctional and highly efficient. Hence, the antenna used in the mobile communication terminal should also be reduced in size and highly efficient.
The antenna for the typical mobile communication terminal as a quarter-wave monopole antenna or a helical antenna protrudes outside the mobile communication terminal, which causes a user's inconvenience in carrying the terminal and a stability-related problem. To address such problems, active researches for an embedded type antenna are in progress.
As antennas are reduced in size and designed as an embedded type, a study on Planar Inverted F Antenna (PIFA) has been actively conducted. The PIFA is widely adapted as an embedded antenna for a portable terminal, by virtue of its simplified processes and planar structure. However, the embedded antenna is merely limited in its size in order to be mounted in a narrow space of the mobile communications terminal. Also, as the antenna is reduced in size, an input impedance has a small resistance and a large capacitive reactance. Here, if the reactance is eliminated by a matching circuit, a narrowband characteristic is exhibited. In addition, the small resistance characteristic may drastically lower a radiation efficiency of the antenna. Furthermore, a thickness of a mobile communication terminal should be concerned in order to mount the antenna therein, which results in limitation in a height of an antenna in the PIFA structure. Hence, the embedded antenna has limitations in obtaining wide bandwidths.
As such, there are physical limitations in making a small and light antenna, which is used in a portable terminal, have a ultra wideband, due to the limitation in the size of a portable terminal.